A significant quantity of coalbed gas is physically bound (or sorbed) within coalbeds. This coalbed gas, believed to be formed during the conversion of vegetable material into coal, and comprises primarily methane (CH4). Because it is primarily methane, coal gas is commonly termed coalbed methane (CBM) as it is referred to herein, although it is sometimes also referred to as Coal Seam Methane (CSM). Typically, more than 95% of the CBM is physically bound (adsorbed) onto the surface of the coalbed matrix. Such CBM can generally only be sold at a profit if the process efficiency is high enough and the costs to produce it are minimized.
However, methane production from CBM fields is known to be both technically and commercially challenging. After investing in the discovery and proving of CBM fields with commercially exploitable reserves, the enterprise must invest in, and then implement and operate a large number of wells that produce at significantly lower volumes than conventional gas wells. The number of wells in the well field could be as low as 50, but as high as several thousand. The enterprise must further implement and operate a plant, pipelines, and equipment and operational support resources to enable the extraction, gathering, compressing, water treatment, dehydration and treatment of the gas, and transportation and transfer (or other disposal) of the gas for sale. This assembly of plant equipment and naturally occurring reservoirs must be operated as a cohesive system of interconnected and interdependent parts. At least some of the system parts act in somewhat non-deterministic fashion, for example the extraction wells, thereby making the regulation of methane from CBM fields difficult.
Conventional control system software for operating CBM fields use low level (e.g. single variable) regulatory control solutions. Single variable control ties one control variable (e.g. temperature or pressure) to one manipulated variable (e.g. valve position or set point). Such control solutions do not have the ability to handle multiple constraints or to write to multiple manipulated variable set points from a single application. Single variable control also cannot coordinate the operation of the separate regulatory controls to achieve a global optimization objective.